Remove current volatile filehandle implementation

The current volatile filehandle implementation does not work well.  It
expires all filehandles on server reboot, which is of dubious value.
There's also facility to let the FSAL set an expire type that isn't
used for anything.

If we do decide we want volatile filehandle support, we could get it
later by letting the FSAL return an EXPIRED error that is propagated
to the user and exposing an expire type as a per-filesystem attribute.
(An upcall to let it blow out an expired handle might be nice, too.)

Signed-off-by: Adam C. Emerson <aemerson@linuxbox.com>
Remove referral code

Referrals do not actually work (there's no code to actually give the
fs_locations attribute to a client).  Even if they did work they
wouldn't work very well, since they have to all be set up at config
time and can only exist within the pseudoFS, and marking a handle as a
referral commits something as always present or always absent.

New referral code will be implemented in 2.1, so we can get the old
stuff out of the way here.

Signed-off-by: Adam C. Emerson <aemerson@linuxbox.com>
Fix shutdown of delayed executor

Signed-off-by: Adam C. Emerson <aemerson@linuxbox.com>
Remove unused PNFS and DELEG per-export options

Signed-off-by: Adam C. Emerson <aemerson@linuxbox.com>
Finish removal of Ganesha managed write buffer

The commit code to push data out of the write buffer and into the FSAL
had already been removed, so if anyone had actually turned this on,
seriously bad things would have happened.

Signed-off-by: Adam C. Emerson <aemerson@linuxbox.com>